1. Field of the Invention
This invention relates to the modification of rigid polyvinyl halide to render such polymers more suitable for use in the preparation of moldings and to improve the physical properties of the polymers, for instance, to improve the impact strength.
2. Description of the Prior Art
It is known from U.S. pat. No. 2,384,947 to blend polymeric vinylidene chloride products with phenol formaldehyde resins including pure phenolic resins and reaction products of phenol with an aldehyde modified by the addition of other substances. Such mixtures provide a polymeric vinylidene chloride product which can be molded or extruded at lower temperatures and pressures than can be the polymeric vinyldene chloride alone. Articles prepared from such compositions retain a high tensile strength and can be used to produce molded articles which are translucent to opaque and have a durable glossy finish.
It is also known to prepare compositions comprising a vinyl resin, plasticizer therefor, and a thermoset phenol aldehyde resin of the novolac type which has been advanced to the insoluble infusible stage, while in an intimate and homogeneous mixture with the vinyl resin and plasticizer (U.S. Pat. No. 2,659,708). Such mixtures are prepared using the phenolic resin prior to its advancement to any substantial extent toward the insoluble, infusible stage and then after an intimate homogeneous mixture has been formed advancing the phenolic resin in the presence of a hardening agent while mechanically working the mixture while hot.
Oxyalkylated novolacs can be prepared from phenol aldehyde condensates by reacting these with mono-oxirane ring compounds, alkylene halohydrins or an alkylene carbonate as disclosed in U.S. Pat. No. 3,538,040.
Polyvinyl chloride usually must be modified, compounded, or copolymerized with other materials to provide processable and useful compositions. For example, when processing polyvinyl chloride on rolling mills, such materials as chlorinated polyethylene and acrylic polymers, such as polymers of methyl methacrylate and ethylacrylate, are added for flexibility, in addition to such materials as plasticizers illustrated by dioctyl phthalate, polypropylene adipate, etc.
The compounding of the polyvinyl chloride compositions is necessary because of the limitations in processability of the polyvinyl chloride. The usual fabrication temperatures for rigid polyvinyl chloride compositions can lead to thermal degradation of the product during extended fabrication periods. At the temperature of extrusion, injection, thermoforming, blow molding and the like, polyvinyl chloride compositions tend to degrade due to the heat instability of the polyvinyl chloride. It is obviously most desirable that polyvinyl chloride should be processable at lower temperature and with shorter cycle times, thereby minimizing changes resulting from thermal degradation. While common plasticizers reduce the melt viscosity of polyvinyl chloride, these materials also flexibilize the composition at service temperatures and thereby adversely affect the physical properties of the composition intended to be rigid at service temperature.
It has now been discovered that the inclusion of oxyalkylated novolacs in polyvinyl chloride provide homogeneous compositions which eliminate or greatly improve upon many of the deficiencies of rigid polyvinyl chloride, without detracting from the desirable physical properties. The oxyalkylated novolacs act to improve the processing characteristics by reducing the melt viscosity of the mixture.